For theoretical analysis, we developed the simulation model of the evolving process of friendship together with the colleagues in the Netherlands. For this research, I wrote the article, "the network formation under the imperfect information", at the Research Bulletin of Konan University in 2002. This research has been done with the colleagues in the Netherlands.For experiential analysis, we collected and analyzed data of students in Japan and the Netherlands on the friendship development. These data were longitudinal ones. For this research, I wrote the article, "Birds of a feather flock together", at the Research Bulletin of Konan University in 2003.We also tried to the analysis of "personal(ego-centric) networks". I wrote the article, "the analysis on the personal networks-about the students of Konan University-", at the Research Bulletin of Konan University in 2004.